CN112924740A - Sampling device based on capacitance isolation - Google Patents
Sampling device based on capacitance isolation Download PDFInfo
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- CN112924740A CN112924740A CN201911235627.4A CN201911235627A CN112924740A CN 112924740 A CN112924740 A CN 112924740A CN 201911235627 A CN201911235627 A CN 201911235627A CN 112924740 A CN112924740 A CN 112924740A
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- isolation
- modulator
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- sampling device
- sampling
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M3/00—Conversion of analogue values to or from differential modulation
- H03M3/30—Delta-sigma modulation
Abstract
The invention provides a sampling device based on capacitance isolation, which comprises: the signal input module is arranged on the primary side and used for receiving the sampling signal; the signal output module is arranged on the side of the secondary side and used for outputting a sampling signal; and a plurality of capacitance isolation modules are connected between the primary side and the secondary side and used for carrying out high-voltage isolation on input and output of sampling signals. The invention adopts the capacitance isolation technology, realizes high-precision current sampling, can realize higher isolation voltage, is less influenced by the change of a magnetic field, and is very suitable for high-isolation and high-precision current detection occasions.
Description
Technical Field
The invention relates to phase current detection in motor driving, in particular to a sampling device based on capacitive isolation.
Background
With the development of science and technology, high-power equipment such as industrial control and power grids usually work by adopting a higher bus voltage.
Referring to fig. 1, taking three-phase motor driving as an example, each phase of current needs to be sampled to provide reference information for generating bridge arm driving signals; the input end of the current sampling device has a voltage signal with a high common mode, the output end of the current sampling device is connected with a low-voltage microcontroller, and in order to ensure safety and block interference, the input and the output of the sampling device must be isolated with high voltage.
At present, isolation technologies mainly include a hall technology, a photoelectric isolation technology, an electromagnetic isolation technology and an inductance isolation technology, wherein a hall sensor is low in precision and poor in linearity, and is difficult to meet the requirement for high-precision measurement, a photoelectric coupler has the characteristics of obvious aging characteristic, low data transmission rate and the like, the electromagnetic isolation technology is easily interfered by magnetic field changes, and the isolation schemes have certain limitations.
Disclosure of Invention
In view of the above disadvantages of the prior art, the present invention aims to provide a sampling device based on capacitive isolation, which is used for solving the problems in the isolation technology of the prior art that the hall sensor has low precision and poor linearity, and is difficult to meet the measurement requirement of high precision; the photoelectric coupler has the characteristics of obvious aging characteristic, low data transmission rate and the like; the electromagnetic isolation technique is susceptible to the problem of interference from magnetic field variations.
To achieve the above and other related objects, the present invention provides a sampling device based on capacitive isolation, comprising: the method comprises the following steps:
the signal input module is arranged on the primary side and used for receiving the sampling signal;
the signal output module is arranged on the side of the secondary side and used for outputting a sampling signal;
and at least one capacitance isolation module is connected between the primary side and the secondary side and is used for carrying out high-voltage isolation on input and output of sampling signals.
In an embodiment of the present invention, the signal input module includes an amplifying unit, a first modulator and a mixer; the signal output module comprises a first demodulator, a digital-to-analog conversion unit and a filtering unit; the input end of the first modulator is also connected with a clock unit;
sampling signals sequentially pass through the amplifying unit, the first modulator and the frequency mixer and then are output to the corresponding capacitance isolation module;
the isolated sampling signal is output to a subsequent circuit after sequentially passing through the first demodulator, the digital-to-analog conversion unit and the filtering unit.
In an embodiment of the invention, the first modulator is a Sigma-Delta second-order modulator.
In an embodiment of the present invention, the clock unit includes a low frequency oscillator and a second modulator disposed at a secondary side; a second demodulator arranged at the primary side;
the output end of the low-frequency oscillator is connected with the input end of the second modulator, the corresponding capacitance isolation module is connected between the output end of the second modulator and the input end of the second demodulator, and the second demodulator outputs a clock signal to the first modulator.
In an embodiment of the present invention, the capacitor isolation module includes two isolation capacitors connected in series, and the isolation capacitors are all on-chip capacitors.
In an embodiment of the invention, the digital-to-analog conversion unit employs a one-bit digital-to-analog converter.
In an embodiment of the invention, the filtering unit is a low frequency filter.
In an embodiment of the invention, the low frequency filter is a fourth-order active filter.
As described above, the sampling device based on capacitive isolation according to the present invention employs the capacitive isolation technology, and can realize high isolation voltage and small influence from magnetic field change while realizing current sampling with high precision, and is very suitable for high isolation and high precision current detection occasions.
Drawings
Fig. 1 shows a schematic wiring diagram of a three-phase motor drive circuit.
Fig. 2 shows a block diagram of the present invention.
Fig. 3 is a block diagram of the clock unit according to the present invention.
Fig. 4 is a schematic wiring diagram of the present invention.
Fig. 5 is a schematic diagram of an ook modulation waveform employed in the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Referring to fig. 2, the present invention provides a sampling device based on capacitive isolation, including:
the signal input module is arranged on the primary side and used for amplifying, carrying out analog-to-digital conversion and modulating the sampling signal and then transmitting the sampling signal to the secondary side; the signal input module comprises an amplifying unit, a first modulator and a mixer; the input end of the first modulator is also connected with a clock unit.
The signal output module is arranged on the side of the secondary side and used for demodulating, converting and filtering the received sampling signal and outputting the sampling signal; the signal output module comprises a first demodulator, a digital-to-analog conversion unit and a filtering unit.
And a plurality of capacitance isolation modules are connected between the primary side and the secondary side and used for carrying out high-voltage isolation on input and output of sampling signals.
Referring to fig. 4, an input terminal of the amplifying unit is connected to a sampling signal, and the sampling signal is a differential signal. And the sampling signal is amplified by a preamp and then input into the first modulator. The resistances of the resistor R1 and the resistor R3 in the amplifying unit are equal, the resistances of the resistor R2 and the resistor R4 are equal, and in order to improve the amplifying precision, the resistors R1, the resistor R3, the resistor R2 and the resistor R4 are selected as high as possible in precision and consistent in linearity.
In order to ensure a high signal-to-noise ratio, the first modulator preferably employs a Sigma-Delta second order modulator. The input sampling signal is modulated by the first modulator, and an analog signal is converted into a low-frequency digital bit stream.
The output end of the first modulator is also connected with a mixer, the low-frequency digital signal output by the first modulator is modulated to high frequency, and on-off keying modulation is carried out.
Referring to fig. 5, the ook modulation scheme mixes the signal to a high frequency, up to several hundred mhz, during the high level period of the signal and does not process the signal during the low level period of the signal.
Each path of differential signal output by the frequency mixer is connected with a capacitance isolation module which is used for carrying out high-voltage isolation on input and output of a sampling signal; the capacitor isolation module comprises two isolation capacitors connected in series, the isolation capacitors are all on-chip capacitors, the on-chip capacitors adopt the uppermost layer and the lowermost layer of multi-layer metal as upper and lower polar plates respectively in a standard Complementary Metal Oxide Semiconductor (CMOS) process, and the silicon dioxide medium in the middle can bear high voltage to complete an isolation function.
Referring to fig. 3 and 4, the input end of the first modulator is further connected to a clock unit, and the clock unit includes a low-frequency oscillator and a second modulator disposed on the secondary side; a second demodulator arranged at the primary side;
and the low-frequency oscillator on the secondary side generates a clock signal, and then the clock signal is transmitted back to the primary side through the second modulator, the capacitive isolation module and the second demodulator to provide a working clock for the first modulator.
Referring to fig. 4, the high frequency digital signal passing through the capacitive isolation module is restored to the original digital bit stream by the first demodulator.
The output end of the first demodulator is connected with the digital-to-analog conversion unit, and the digital-to-analog conversion unit adopts a one-bit digital-to-analog converter.
The output end of the digital-to-analog conversion unit is connected with the filtering unit, the filtering unit is a low-frequency filter, and a four-order active filter is adopted for fully filtering high-frequency signals and ensuring high linearity and low distortion.
The original digital bit stream is subjected to amplitude conversion through a one-bit digital-to-analog converter to obtain another part of gain, and finally, the signal is recovered into an analog signal through a high-order active filter and is output to a subsequent circuit;
the closed loop gain of the pre-operational amplifier is A1-R2/R1, after amplitude conversion is carried out by the digital-to-analog conversion unit, the obtained gain is A2-Vdac/Vsdm, and a Sigma-Delta second-order modulator and a fourth-order active filter are both unit gains, so that the total gain of the amplifier is A1-A2.
Vsdm is a reference voltage of a Sigma-Delta second-order modulator, Vdac is a high-level reference voltage of a single-bit digital-to-analog converter, and the high-level reference voltage is generated by the Sigma-Delta second-order modulator and an internal reference of the single-bit digital-to-analog converter.
In summary, the sampling device based on capacitive isolation provided by the invention adopts the capacitive isolation technology, realizes high-precision current sampling, can realize higher isolation voltage, is less influenced by the change of a magnetic field, and is very suitable for high-isolation and high-precision current detection occasions. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (8)
1. A sampling device based on capacitive isolation, comprising:
the signal input module is arranged on the primary side and used for receiving the sampling signal;
the signal output module is arranged on the side of the secondary side and used for outputting a sampling signal;
and at least one capacitance isolation module is connected between the primary side and the secondary side and is used for carrying out high-voltage isolation on input and output of sampling signals.
2. The capacitive isolation based sampling device of claim 1, wherein: the signal input module comprises an amplifying unit, a first modulator and a mixer; the signal output module comprises a first demodulator, a digital-to-analog conversion unit and a filtering unit; the input end of the first modulator is also connected with a clock unit;
sampling signals sequentially pass through the amplifying unit, the first modulator and the frequency mixer and then are output to the corresponding capacitance isolation module;
the isolated sampling signal is output to a subsequent circuit after sequentially passing through the first demodulator, the digital-to-analog conversion unit and the filtering unit.
3. The capacitive isolation based sampling device of claim 1, wherein: the first modulator is a Sigma-Delta second order modulator.
4. The capacitive isolation based sampling device of claim 2, wherein: the clock unit comprises a low-frequency oscillator and a second modulator which are arranged on the secondary side; a second demodulator arranged at the primary side;
the output end of the low-frequency oscillator is connected with the input end of the second modulator, the corresponding capacitance isolation module is connected between the output end of the second modulator and the input end of the second demodulator, and the second demodulator outputs a clock signal to the first modulator.
5. The capacitive isolation based sampling device of claim 1, wherein: the capacitance isolation module comprises two isolation capacitors connected in series, and the isolation capacitors are all on-chip capacitors.
6. The capacitive isolation based sampling device of claim 2, wherein: the digital-to-analog conversion unit adopts a one-bit digital-to-analog converter.
7. The capacitive isolation based sampling device of claim 2, wherein: the filtering unit is a low-frequency filter.
8. The capacitive isolation based sampling device of claim 7, wherein: the low-frequency filter adopts a fourth-order active filter.
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| CN201911235627.4A CN112924740A (en) | 2019-12-05 | 2019-12-05 | Sampling device based on capacitance isolation |
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| CN204967819U (en) * | 2015-09-21 | 2016-01-13 | 中国神华能源股份有限公司 | Synchronized clock controlling means and distributed synchronous sampling system |
| CN106100682A (en) * | 2016-08-11 | 2016-11-09 | 广州金升阳科技有限公司 | Single channel, multiple signals isolation transmission system and full duplex communication system |
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| CN109995356A (en) * | 2019-05-20 | 2019-07-09 | 上海客益电子有限公司 | A kind of signal-isolated transmission circuit based on capacitor |
| CN110061707A (en) * | 2019-04-25 | 2019-07-26 | 电子科技大学 | A kind of isolated amplifier circuit based on Sigma-Delta modulation system |
| US20190278245A1 (en) * | 2018-03-07 | 2019-09-12 | Texas Instruments Incorporated | Crosstalk generation and detection for digital isolators |
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2019
- 2019-12-05 CN CN201911235627.4A patent/CN112924740A/en active Pending
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4438523A (en) * | 1980-11-27 | 1984-03-20 | Siemens Aktiengesellschaft | Differential digital modulation and demodulation system with an analog signal-dependent sampling clock |
| CN1953438A (en) * | 2006-10-26 | 2007-04-25 | 西安电子科技大学 | Binary frequency shift key controlled filling type digital demodulation method |
| CN101667010A (en) * | 2009-09-28 | 2010-03-10 | 浙江大学 | GPS synchronous clock carrier power source |
| CN104113501A (en) * | 2014-06-19 | 2014-10-22 | 北京科技大学 | Modulator, demodulator, modulation method and demodulation method for low-frequency magnetic induction communication |
| CN204967819U (en) * | 2015-09-21 | 2016-01-13 | 中国神华能源股份有限公司 | Synchronized clock controlling means and distributed synchronous sampling system |
| CN205721226U (en) * | 2016-05-04 | 2016-11-23 | 中国船舶重工集团公司第七一○研究所 | A kind of signal acquisition module for fast arc extinction device |
| CN106100682A (en) * | 2016-08-11 | 2016-11-09 | 广州金升阳科技有限公司 | Single channel, multiple signals isolation transmission system and full duplex communication system |
| US20190278245A1 (en) * | 2018-03-07 | 2019-09-12 | Texas Instruments Incorporated | Crosstalk generation and detection for digital isolators |
| CN110061707A (en) * | 2019-04-25 | 2019-07-26 | 电子科技大学 | A kind of isolated amplifier circuit based on Sigma-Delta modulation system |
| CN109995356A (en) * | 2019-05-20 | 2019-07-09 | 上海客益电子有限公司 | A kind of signal-isolated transmission circuit based on capacitor |
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